Earline Hilda Castillo-Binger and Mary Coyne tending the vegetables at the co-op’s gardens in Lambeth, south London.
Photograph: Souvid Datta for the Guardian

Despite the rain, Mary Coyne is helping Earline Hilda Castillo-Binger with the weeding. “See, Mary, these onions are coming up,” says Castillo-Binger. “And the avocado plant is doing well.” These women are not professionals, but are a new breed of gardeners who discovered their love of plants and getting their hands dirty from an unusual source: their local doctor’s surgery.

The Lambeth GP Food Co-operative was launched in 2013 at Brockwell Park surgery, south London. With £160,000 in funding from the clinical commissioning group (CCG) and Lambeth council, 11 GP surgeries across the borough have turned unused outdoor space into gardens for patients to grow fruit and vegetables. GPs and nurses refer patients who are lonely and socially isolated, have a long-term condition and/or have mental health problems.

Coyne, 60, was referred to the co-op in November by a practice nurse at the Lambeth Walk practice, following a breakdown. Initially unsure about the scheme, like fellow patient Castillo-Binger, she is now one of the keenest members, turning up weekly to weed, water the plants and sow seeds in the surgery’s narrow garden. “It’s making me eat more vegetables,” she says.

The aim is to harness the physical and mental therapeutic benefits of gardening while growing more local produce. David Wickstead, a GP partner at another participating surgery, says the scheme has clinical benefits too. “It’s good for us [doctors], because the danger with mental health patients is that you stick to medication – changing it, changing the dosage, trying a new therapy and so on. So the fact that we have something else with a different approach is fantastic.”

It is also an easy way for doctors to help combat loneliness. “I love it – it keeps me active,” says Millicent Morris, 71, from Camberwell. “I enjoy meeting the others in the groups and growing the different seeds.”

More than 200 mostly older patients have got involved, although the number of regular attendees is much smaller, as many turn up only in warm weather.

“To the best of our knowledge, the Lambeth GP Food Co-op is the only community-led health co-operative of its kind in England,” says Ed Rosen, its director.

Jim Dickson, cabinet member for health at Lambeth council, believes the project will improve residents’ physical and mental health. “The GP food co-op is an initiative aimed at delivering real, long-term and sustainable benefits to the health of Lambeth residents and our environment.”

Lambeth is the eighth most deprived borough in London. Just over 12% of its 318,000 population have a long-term health condition. Hunger is also a growing problem: according to the Trussell Trust, nearly 105,000 people used food banks in London in the year to April 2015, up just over 10,000 from the previous year. One of the attractions of the co-op is that its members get to eat the food they produce.

Millicent Morris, Daphne Foster and Bruno Lacey pick rocket. ‘More than 200 mostly older patients have got involved, although some only turn up in warm weather.’ Photograph: Souvid Datta for the Guardian

Rosen wants to go further. Tomorrow, to mark NHS sustainability day, the co-op announces a new venture: selling its produce in King’s College hospital. The hospital had already established a working relationship with Lambeth GP food co-op, by providing land for a nearby GP practice’s patients to garden in as the surgery’s premises had minimal outside space. Now members of the co-op will run a fruit and vegetable stall in the hospital’s restaurant, with any profits reinvested in the co-op.

The market stall is a joint venture with Medirest, the hospital’s catering supplier. Lisa Hunter, Medirest’s catering dietitian, says a key element of the government’s new hospital food standards is that “trusts need to make the food served to patients healthier and more sustainable”. “We hope that our collaboration with Lambeth GP Food Co-op will allow us to do this by increasing the availability of locally grown fruit and vegetables to staff, visitors and patients.” Rosen hopes that, eventually, Medirest will be able to use the produce grown by the food co-op to prepare hospital meals.

Meanwhile, the co-op keeps on growing. Grantham Place practice is the newest surgery to sign up and patients and GPs will start gardening from next month. The surgery will target three groups: members of the patient participation group, those with chronic diseases or mental health problems and people who are isolated, who “don’t see anyone locally, stay at home a lot, muscles atrophying and cooking for one, so eating a lot of processed food”, says Vikesh Sharma, one of Grantham’s GP partners. He adds that the food co-op will “make us more accessible and encourage us doctors to leave our rooms. And that can only be a good thing.”

“It provides the only platform for me as a GP to see my patients outside the physical walls of my surgery, reinforces the idea of community doctors and reminds me of the wider context of what being healthy actually means. It allows patients a more relaxed way to engage with their GP surgery (as opposed to a harried 10 minute appointment or waiting half an hour on the phone). It helps build trust and relationships between the doctor and patient that is so vital to the way a GP provides continuity of care.”But with local authority cuts and very tight NHS budgets, the co-op’s expansion plans depend on being able to secure ongoing funding. A community share issue is planned for next month and Rosen is awaiting confirmation of one-year “transitional funding” of £45,000 from the CCG. The council will not be providing further funding but will continue to support and champion the co-op, says Dickson.

Meanwhile, the scheme needs to quantify the difference it makes. So far no independent clinical analysis has been done, but anecdotally, doctors say participants’ health has improved. “The people who come here to garden see us less often,” says Raj Mitra, a GP partner. Interviews by two nutrition and dietetics undergraduate students with 10 patients involved with the co-op found that the biggest benefit was social, in particular reducing isolation, as well as providing a means of gentle exercise. But while four participants said they had increased their fruit and vegetable consumption since joining the co-op, the majority did not change their eating habits.

But for Coyne, the difference is palpable. In addition to discovering she liked pumpkins and eating more vegetables, she says the co-op has made a difference to her mental health. “I’ve made friends here. It’s given me back my confidence.”